1. Field of the Invention
The present invention relates to a dust-proof fabric. More particularly, the present invention relates to a dust-proof fabric useful for preparing dust-proof clothing to be used in clean rooms, for example, industrial clean rooms, biological clean rooms and surgical operation rooms, which are effective for preventing contamination of the human body or specific articles with dust generated from machines and human personnel.
The dust-proof fabric of the present invention generates dusts therefrom in a very reduced amount and can collect dust at a high efficiency. Also, the dust-proof fabric of the present invention exhibits an antistatic property which prevents excess attraction of dust and prevents breakdowns of semiconductor devices.
2. Description of the Related Art
It is known that to prevent undesirable generation of dust from clothing of workers or operators in industrial clean rooms and other clean rooms by use of dust-free clothing (inclusive of sterile clothing). The dust-free clothing is produced from woven or knitted fabrics consisting of synthetic filament yarns or nonwoven fabrics consisting of spun bonded continuous filaments. Also, it is known to prevent undesirable adhesion of dust on the dust-free clothing by antistatic treatment applied to the dust-free clothing.
With recent increase of precision, integration, and miniaturization in the semiconductor industry and precision machine industry and in the fields of the bioindustry and medical industry, clean rooms have come into broad use. It is especially required at the present time that the cleanliness of air in a clean room be further increased. For example, in the field of semiconductors, the integration degree in LSI's is being increased to 256 K-bits from 64 K-bits. It is expected that the integration degree will be elevated to 1 M-bit (megabit) or higher in the not too distant future. It is ordinarily considered that the air cleanness degrees of clean rooms required for these integration degrees are class 1000-100, class 100-10, and class 10 or lower. It also is considered that the size of dust to be removed becomes smaller as the air cleanness is elevated. Namely, minute dust or bacteria cause defects in products. Hence, the higher the air cleanness, the more important the prevention of generation of dust. Accordingly, with elevation of the cleanness of a clean room, enhancement of the dust-preventive effect in dust-free clothing is required.
The largest dust-generating sources in a clean room are the human personnel themselves. The contamination level in the clean room is elevated by dust generated from the personnel. The dust-generating sources of human personnel include (1) the physical bodies, (2) undergarments, and (3) outer dust-free clothing. Generation of dust from the clothing can be greatly reduced by using a filament yarn and periodically cleaning the dust from the clothing. The main sources of dust are therefore the body and undergarments of the personnel. Accordingly, it is necessary that dust generated from the body or undergarments be prevented from being discharged outside.
Therefore, the clothing should be made or dust-proof fabric which prevents discharge of dust outside from the clothing. Of course, it must be excellent in adaptability, durability, and comfort. As means for preventing discharge of dust, there has been proposed a fabric with a low dust permeability, that is, a high dust-collecting property (high filtering property). Conventional woven and knitted fabrics, however, have a high dust permeability (low dust-collecting efficiency). Certain spun-bond non-woven fabrics have low dust permeability, but they also have a paper-like stiff touch and poor washing resistance.
Recently, as means for reducing the dust permeability of a woven or knitted fabric and preventing discharge of dust, the dust-free clothing has been made from a fabric obtained by resin-coating a woven or knitted fabric of synthetic filaments or a fabric obtained by laminating a film on a woven or knitted fabric of synthetic filaments. According to this technique, the fabric is coated, e.g., with a water-proof moisture-permeable resin such as a polyurethane resin to reduce the air permeability while maintaining a certain moisture permeability. Clothing of this type does not allow permeation of air, and resists, permeation of dust. However, such clothing is is defective in various points. For example, since the moisture permeability and air permeability are poor, the clothing becomes uncomfortable on wearing. A resin-coated (or laminated) fabric is also ordinarily poor in durability, washing resistance, and abrasion resistance. Clothing to be used in a clean room is frequently subjected to dry cleaning, but a water-proof moisture-permeable resin is ordinarily poor in dry cleaning resistance. In short, a fabric for dust-free clothing, which is satisfactory in dust-collecting efficiency, wearing properties (moisture permeability and air permeability), wearing durability, washing resistance, abrasion resistance and antistatic property has not been developed.